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Date: Thu, 4 Dec 2025 14:10:25 +0100
From: Christoph Hellwig <hch@lst.de>
To: Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>
Cc: Christoph Hellwig <hch@lst.de>, Pavel Begunkov <asml.silence@gmail.com>,
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	Vishal Verma <vishal1.verma@intel.com>, tushar.gohad@intel.com,
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Subject: Re: [RFC v2 01/11] file: add callback for pre-mapping dmabuf
Message-ID: <20251204131025.GA26860@lst.de>
References: <cover.1763725387.git.asml.silence@gmail.com> <74d689540fa200fe37f1a930165357a92fe9e68c.1763725387.git.asml.silence@gmail.com> <7b2017f4-02a3-482a-a173-bb16b895c0cb@amd.com> <20251204110709.GA22971@lst.de> <0571ca61-7b17-4167-83eb-4269bd0459fe@amd.com>
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On Thu, Dec 04, 2025 at 12:09:46PM +0100, Christian König wrote:
> > I find the naming pretty confusing a well.  But what this does is to
> > tell the file system/driver that it should expect a future
> > read_iter/write_iter operation that takes data from / puts data into
> > the dmabuf passed to this operation.
> 
> That explanation makes much more sense.
> 
> The remaining question is why does the underlying file system / driver
> needs to know that it will get addresses from a DMA-buf?

This eventually ends up calling dma_buf_dynamic_attach and provides
a way to find the dma_buf_attachment later in the I/O path.